1. Field of the Invention
The present invention relates to an image display apparatus including a light emitting unit with a plurality of divided light-emitting regions and a method for controlling thereof.
2. Description of the Related Art
Recently, light-emitting diodes (LEDs) have been used as a light emitting element for a backlight of an image display apparatus since LEDs have long life and consume less power. A light emission amount of an LED can be controlled by repeating ON/OFF of current passing through the LED at a constant frequency to change an ON/OFF ratio and a current value passing through the LED.
The LED has a property that a light-emitting characteristic differs according to an individual difference, aged deterioration, and the like. In a case where a plurality of LEDs are used as a light source of the image display apparatus, since the light emission amount differs between each LED, the light emission amount varies between the LEDs. To solve the above problem, Japanese Patent Laid-open Publication No. 2007-294385 discusses a backlight device capable of adjusting variation in the light emission amount per a chip including a plurality of LEDs. A process for adjusting the light emission amount of the light emitting element to a predetermined value in the backlight device and the like is hereinafter referred to as “light emission adjusting process”.
In a liquid-crystal projector, a fan works to remove heat in the housing of the projector after power to the lamp of the projector is turned off. Japanese Patent Laid-open Publication No. 2003-121929 discusses a technique that progress until the fan is shutdown is shown to a user by changing a luminescent color or a light-emitting state of the LED to indicate how long it takes before the fan is shutdown after power to the lamp is turned off.
When the light emission adjusting process is performed, the light emitting element of the backlight is arbitrarily lit up to adjust the light emission amount of the light emitting element of the backlight. The light emitting element for adjusting the light emission amount is lit up as needed, but the light emitting element other than those unrelated to the adjustment of the light emitting element may not be lit up. The light emission amount can be adjusted more accurately if the light emission element unrelated to the adjustment of the light emission element is not lit up in a case where only the light emission amount of the light emitting element to be adjusted is required to be detected.
Therefore, only a part of the light emitting elements may be lit up in the backlight during the light emission adjusting process, so that a normal image that requires luminescent colors of red (R), green (G), and blue (B) sometimes cannot be displayed. During the light emission adjusting process of the back light, if the light emitting element to be adjusted is sequentially changed, a light-on area and a light-off area of the light emitting elements change over time. Therefore, in a case where an image representing progress of the light emission adjusting process (e.g., how far the light emission adjusting process goes) is displayed, an image of the area in which the back light is lit out may not be recognized. To provide the progress by using the LED in a manner as discussed in Japanese Patent Laid-open Publication No. 2003-121929, the LED is required to be provided at a position other than the display screen as well as a correspondence between a light emission pattern of the LED and the progress of the light emission adjusting process needs to be recorded, so that the user cannot grasp information of the progress and the like with ease.